NO830507L - FORK IMPULS SIGNAL OPERATED PHONE CONTROL DEVICE. - Google Patents

Description

FORK PULSE SIGNAL OPERATED TELEPHONE CONTROL DEVICE

IN THE TECHNICAL AREA

in

The present invention relates to a reasonable device which is plugged into the subscriber line of any known telephone (e.g. rotary dial telephone or keypad), so that the telephone can be controlled by hook flash signals which are selectively initiated by the receiver of an incoming call, to make it possible for the recipient to hang up on the phone, while Idet fo! existing calls are temporarily put on hold. The present control device responds to a special and predetermined sequence of fork impulse signals, which are generated by means of the conventional fork electrical contacts in! a telephone for activating a hold circuit and thereby putting the current call on hold. j

As those skilled in the art will be familiar with, it is often desirable to only

i ne control the circuits of a telephone in the home so that the telephone user can easily put an incoming call on hold

i without disconnecting the caller. In this way, if the recipient is interrupted by an incoming call, he can have time to complete his tasks before taking care of the call. Should have! If the recipient further wishes to receive the call in another, more comfortable place (e.g. on an auxiliary device), can receive-! In clean without further ado move to this place before he re-! takes the call.. !

F1 clay telephone controls are available, with whi; lke'j a user can put an incoming call on hold. I| US Patent Application Serial No. 288 397 , filed 26. 01 .1981', there is described, for example, a reliable, mountable, electronic telephone holding circuit, with the help of which the recipient 1 of an incoming call can hang up on the telephone

In the phone fork while the current call is temporarily put on hold, the call can be resumed at a later time or from another location. The holding device mentioned there is particularly adapted for detachable connection to the phone's fork.

Other examples of available telephone control devices which can place the circuits for an assigned telephone in a hold state include devices which are selectively operated by gaffei-

impulse signals generated by the phone's jack socket. More 1 i i precise, special illustrations of such fork-impulse-

be: served telephone control devices can be found in one or more of the following US patent documents: | in ! in

i1Di e • conventional telephone control devices for holding are j :however iI often characterized by the wood or several of the following deficiencies!. j More precisely, some conventional telephone control devices are typically connected directly to the telephone. Such an integrated coupling can prove to be unreliable when needed j ! f! oi r installation, repair or replacement of devices gen. That is, the telephone circuits must be modified to up-| ; i t take; the connection of the control device. In addition, space requirements can; know to be undesirably maximized, if the control device is to be connected to the housing of the telephone set.

Other conventional telephone control devices are connected at each device in a multi-device network. Thus, a telephone control device must be used at each device in order for a user j to be able to accept an incoming call at a first device and, after putting the call on hold, to be able to resume the call at another or an auxiliary device. Such conventional systems are both ineffective and relatively expensive to realize, i

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In addition, other conventional telephone control devices

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<:>; schemes do not include funds for automatic termination of

■a hold state in case the user inadvertently puts the téléifone circuits into a hold state indefinitely. The lack of a means of terminating a hold condition could undesirably cause the user's telephone circuits to continuously

! i is busy, so the user is unable to answer any further incoming calls. in

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■Further conventional telephone control devices, and particularly those that are selectively operated by means of fork contact-generated j j rected fork impulse signals, do not include reliable meansj for distinguishing between a hold order and other fork contact operated orders, by means of which a user may otherwise ' wish to get in touch with the operator at the central tele-! fan station. Thus, by operating the telephone jack socket with one in an incorrect sequence, a user may inadvertently cause a transmission or an interruption of an existing connection,!

i i;instead of putting the call on hold. ! • ' i

BRIEF DESCRIPTION OF THE INVENTION

A fork-impulse signal-operated telephone control unit is described in ! in an arrangement which responds to a specific and predetermined sequence of user-triggered fork pulse signals, thereby selectively activating a hold circuit and allowing a telephone call to be placed on hold. The steering device can be connected to any conventional one

telephone (e.g. rotary dial telephone or keypad telephone) by TIP 1 i and RING telephone conductors which are adapted to a central telephone j station and where well-known telephone contacts are connected like this! that the need for unwanted switching of the telephone essentially; just gets eliminated. The control device comprises a plurality of j : signal timing controls and counters which both respond to the number i and the length of fork impulse signals generated in a specific time interval.

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More precisely, a counter (56 and 70) is provided to count the number of fork impulse signals generated by the telephone's

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' 1 |'gaf f electric contacts . When the number of counted fork electric impulse signals I i

I corresponds to the number of fork impulse signals that make it up

In i : in particular sequence, an output signal is provided to activate the hold circuit and to put a call on hold. 1 l i<!>i [There are arranged first (8) and second (14) time controls for ' must! ling of the pulse length duration of each fork pulse signal. First and second time control are connected so that they I . I I hi internalizes the signal counter's count and prevents activation<!>of the ;holding circuit in the event that the length of a fork pulse signal 1 is either less or greater than the respective set| in times. A third timer (16) is arranged to measure<1>in Idi 1 a time taken to complete the particular sequence■1 I of !fork impulse signals. If the time taken to complete the special sequence exceeds a set time after generation of a first fork pulse signal, the third j I timer will generate an output signal that causes the counter to ' j s.tart its signal count again. A fourth timer (20) is arranged to measure the time after completion of the special sequence of fork pulse signals. If the time .which! If after completion of the special sequence exceeds a predetermined time, the fourth timer 1 will produce an output signal to de-energize the holding circuit and cause the counter to restart its signal count. A five-j i te time management (10) is arranged to measure the time fork- i

in 1 the contacts are in the free or open position before the particular in sequence of fork impulse signals occurs. If the fork-i contacts are in the free position for less than the set .time before the special sequence occurs, fifth j timing control produces an output signal to inhibit activation of the hold-j circuit, so that inadvertent activation of the hold circuit due to bounce or random rocking back and forth-> geez of fork contacts is prevented.

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BENEFICIAL EFFECTS OF THE INVENTION j

It is thus a main purpose of the present invention! i i j ;åj to provide a fork impulse-operated telephone control device-<;>nii ng, where a user can easily and conveniently set a request - : ; making calls in the hold state by activating the fork contact contact'; Iij's phone according to a specific work sequence.

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i Another object of the present invention is that the control device is adapted for interface connection to which

j i soIm preferably known telephone (e.g. rotary dial telephone or mobile phone) with optional design. in

Another object of the present invention is that the control system should be electrically connected at an optional, suitable place in a subscriber line (ie via which the signals are sent from the central station), instead of being connected to the internal telephone circuits, so that the telephone circuits do not \ !need extra wiring or modification. By connecting the control device to a subscriber line, a single control device can also be appropriately interfaced with each telephone that forms a multi-device network.

!! Y: a further object of the present invention is afr<i>

1 the control device is provided with time control and feedback devices, with which the user's telephone circuits aut' o- i! is automatically reset for the reception of new incoming calls, if the user inadvertently puts their telephone circuits in a hold state for more than a set period of time. IN

A further object of the present invention is for the control device to respond to a specific sequence of fork contact generated fork impulse signals which are selectively initiated by the telephone user, so that a user's order which has tii

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intent to put the telephone circuits in a hold state can easily be distinguished from other user orders which are made with fork impulses

Another object of the present invention is that the control device includes connections which are produced according to conventional microelectronic technology, so that space use and production costs can be kept to a minimum. '

Further objects and advantages of the invention will become apparent

; in the following description and the new features that characterize the invention are precisely stated in the following claims.

i BRIEF DESCRIPTION OF THE DRAWINGS

'■ The present invention can be more easily described with reference to the attached drawings, where

fig. 1 is a block diagram illustrating the fork impulse signal-triggered control device that constitutes the present invention,

in fig. 2 is a diagram of a preferred circuit for implementation I of the control device according to fig. 1, !I

<!> in fig. 3 illustrates the logic used for control and the circuit according to fig. 2, i

fig. 4 is a time chart illustrating different signal levels that are generated when the control device according to fig. 1 in stays! used to put an existing phone call on hold, and I

in fig. 5 is yet another time chart illustrating various ; signal levels that are generated when certain existing condition- ; is not met, so that an existing telephone call is not put on hold.

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DESCRIPTION OF THE PREFERRED EMBODIMENT:

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Reference is now made to the drawings, where the telephone control device which constitutes the present invention is described in detail. The drawing's fig. 1 shows a block diagram which shows in detail the interconnection of the present control device with the telephone line for a subscriber, via which line control signals are sent to and from a central telephone station. Each of a number of possible telephones (e.g. either rotary dial telephones or keypad telephones), which are interconnected to form a user telephone network 1, is connected to a subscriber line. As fjag-fplk will be familiar with, subscriber 1 often includes the jet pair of conductors 2 and 2', denoted TIP and RING. Each conductor is assigned to a respective fork contact 3 and 3', so that the fork| impulse control signals can be sent via this. .According to the present invention, the above-mentioned telephone control device comprises a circuit which is interconnected with the subscriber line to enable a telephone user to put a current call on hold without breaking the connection, so that the call can be resumed at a later time and/or from somewhere else (ie a secondary device). As described in more detail below, the holding circuit is adapted for selective action when the telephone user initiates a particular sequence of fork pulse signals by depressing and then releasing fork contacts 3 and 3<1>. As an example and in a preferred embodiment of the invention, the signal sequence affecting the holding circuit comprises a pair of successively generated forks --■-! in fault impulse signals. The signal duration (pulse width) of each g^ffel impulse signal is greater than approx. 150 milliseconds, more less than approx. 750 milliseconds. Furthermore, the sequence as

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signals and the time control which acts as a limitation only in ! „ i I constitutes a preferred example of a pulse train which is suitable for operating the present holding circuit. However, this hL1 circuit can be modified to respond to other fork and pulse signal sequences. j i j The reasons why the preferred fork-impulse signal sequence j i jut1set for temporal limitations will now be discussed. The pulse duration of a single fork pulse signal must be long enough (e.g. at least 150 milliseconds) that a fork pulse signal for hold control can be distinguished from a dial pulse (such as that generated when dialing the number on a rotary dial telephone) and fast, repeated end signals (onj--hook—sig-na ls)- which - are used for - to-s ig na lize- to—-telef onopera-

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the signal pair must be completed within an appropriate time interval (e.g. 4 seconds) to distinguish an intentional hold operation from an inadvertent operation of the telephone contact. That is to say, the user is given the opportunity to change his mind and thus stop the hold order by not completing the special sequence of fork impulse signals within the fixed time interval.

The control device mentioned here includes a conventional! djiodebro-1 ikerett 4, which has opposite ends connected to the circuit wires 5 and 5'. Circuit lines 5 and 5' are connected together with TIP and RING conductors 2 and 2' for the subscriber line v.! ed the user's telephone network 1 in a way that will be discussed in more detail in connection with fig. 2. below. A third end a! v the rectifier bridge 4 is connected for outputting an input signal to an electrical comparator 6. The comparator 6 may comprise a conventional half led is not bridged, e.g. one with chip number LM 311, manufactured by National Semiconductor Corporation. The comparator 6 is used to sense the voltage across circuit leads 5 and 5'. More precisely, the line voltage will be j; approx. 50 volt direct current when the microphone or handset rests on the fork or when the fork electrical contacts 3 and 3' are depressed. | I But when the telephone receiver is lifted off and the fork f electrical contacts are1 . released, the line voltage drops to approx. 6 volts DC-j j nging. The comparator 6 is adapted to form an output signal pl; (denoted SWHOOK) with one of the two signal levels, depending on the position of the fork contacts 3 and 3' and correspondingly, voltage between lines 5 and 5'. j

The IUt signal SWHOOK from the comparator 6 is applied to a conventional signal delay device 8. The delay device 8 is mechanized according to conventional techniques to introduce a specific delay (e.g. 150 milliseconds) I I --in the time period in which a signal can sent through it. The time delay that the delay device 8 introduces corresponds to the smallest fork pulse signal width, as defined above for .

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l The output signal (denoted OFHOOK) from the delay device 8 is applied to the respective input terminal for each of a multiple

..time controls 10, 14 and 16 and a digital dif f erensiator ll2. As an example, first timer 10 may comprise a conventional semiconductor chip, e.g. the one with chip number NE 555

which is manufactured by National Semiconductor Corporation. The time control 10 is triggered by the output signal OFHOOK from the delay device 8, and is, as most clearly illustrated in fig. 4', adapted to provide a logically true or relatively positive output signal level (denoted OPEN ) approx. one second 1 (denoted approximately I I after the telephone receiver has been lifted from the fork and the contacts 3 and 31 have been released. The output signal from the timer 10 remains

logically true until something more than one second after the telephone receiver is placed back on the fork, where the fork contact nej

is suppressed. At this time, the timing controller 10 provides a logically false or relatively negative output signal level. The purpose of the timer 10 is to eliminate the possibility of an unintended or false holding condition. Such a condition could occur as a result of either a prellencle On-hook contact (during lifting or placing the handset jfrom/on the telephone fork) or a voltage change which is applied to the telephone circuits immediately before and during generation ! of a ringing signal there. The output signal OPEN from the timing controller jlO is transmitted to a logical control block 18, and its delays

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will be discussed in more detail below in connection with fig. 3'. IN

:The digital differentiator 12 may comprise a conventional

■ i iI hå. semiconductor chip, as one half of chip number 74123, manufactured by National Semiconductor Corporation. The digital jdifferentiator 12 is triggered by the output signal OFHOOK from the delay device 8 and is adapted to generate an output signal consisting of a control monopulse with a relatively true logic level each time the hook is lifted from the fork and fork-

contacts 3 and 3' are released. The monopulse signal from the digital differentiator 10 is sent to the control logic 18 before thereby setting or releasing the logic for controlling the operation of the holding circuit, which constitutes the present telephone control device.

j I The second timing control 14 may comprise a conventional hajlv- \ leader chip, as a half of the above-mentioned chip number | 74123. The time control 14 is triggered by the output signal OFHOOK. from the delay device 8 and is adapted to generate an output signal (designated PULSE DELAY), which consists of a control monopulse. As best illustrated in fig. 4, the control monopuIsen has a relatively true logic level every time the handset is placed back on the fork or when the fork contacts 3 and 3' are pressed down for more than 150 milliseconds. The IM- j PULSE DELAY out signal from the timing control 14 goes trjl in the 'control logic 18. The pulse width (e.g. approx. 750 milliseconds)

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thus breaking an existing call. | in

j Third timing control 16 may comprise a conventional semiconductor chip, such as a half of the above-mentioned chip number 741123 J

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■ The time control 16 is triggered by the output signal OFHOOK from the front of the sink device 8 and is, as most clearly illustrated in fig. 4, adapted to generate an output signal (designated j

4SEK) which has a relatively true logic level and a pulse width: 1 i

■of approx. 4 seconds, shortly after the handset has been placed on its hook ' t eli ler when contacts 3 and 3' are pressed down. The output signall ! from: the timing control 16 goes to the control logic 18 to prevent a <:>false holding condition, which could otherwise occur when changing gai f- ■1

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error impulse in the above two-impulse sequence occurs later than |

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',4: seconds after generation of the first impulse or when the i i i :second impulse is not generated at all. More precisely, the output signal from the timer 16 is utilized to reset part of the control logic 18 in the event that the prescribed fork pulse signal sequence is not completed within a time period.

! j i ' tervall in 4 seconds. ... >

■ The output terminal from the central logic 18 is connected to give an output signal (denoted HOLDFF) from there to a fourth timer 20. The timer 20 may comprise a semiconductor chip, such as the one formed by connecting a half of chip number NE 556 with chip number 7493 ; both chips are manufactured by National Semiconductor Corporation. As most clearly illustrated in fig. 4, the time management is triggered 20 jav

the output signal HOLDFF from the logic 18 immediately after completion of the prescribed fork impulse signal sequence, the timer 20 generates an output signal having a relatively true logic level. The output signal from the time control 20 j

; is returned for resetting a part of the control trigger 18, so that a holding state is thus automatically terminated, every time the duration of the holding state exceeds the Jva-j ' rgity of the time control's output signal. The pulse width of the output j: signal from the time control 20 is selected to an appropriate value (e.g. approx. 6 minutes). With the help of the timer 20, the user's telephone circuits can thus be made available for receiving new incoming calls in the event that the user forgets to end the hold state for more than 6 minutes. I i ; i il M i ;Another output terminal from the control logic 18 is connected for ! in; li ;■ to| issue an output signal (denoted HOLD) therefrom to a hold circuit ' 22. The hold circuit, which will be discussed in more detail below; in connection with fig. 2, can be triggered selectively, because therefore ! o make it possible for a telephone user to hang up; ,on the fork while an existing call is temporarily (for min-! i re than 6 minutes) put on hold, so that the call ', ;>can be resumed at a later time and/or at another | ;place. As most clearly illustrated in fig. 4, trigger holdkr.et-<1>I ! 1 ;then after the prescribed hook pulse signal sequence :has been completed and the user places the telephone receiver back on the :hook to thereby depress the hook contacts 3 and 3'. An output terminal for the control circuit 22 is connected to an electrical connection point between the rectifier bridge 4 and the signal converter. |parator 6. ;I ;A third output terminal for the control logic 18 is connected to a tone generator 24. The tone generator 24 may comprise a kbn-vI ential semiconductor chip, such as that formed by the samein<->;kpI oropdluinsg erat v of a Naog tioen nahl aSlv embicroinkdkuec, tohvr eCr omrped oranutmimoner . UNE t-s5i5g6 n'|iaog-let (denoted TONE) from the tone generator 24 is an audio signal which can be heard by both the caller and the receiver of a telephone call, to indicate that the call is being placed on hold. The Ui t signal TONE is emitted from the tone generator 24 to a conventional audio amplifier 26, which will be discussed in more detail in connection with fig. 2. Consequently, an augmented lyi becomes d-<!>; u: tsignal connected to circuit wires 5 and 5' by means of ! a conventional output audio transformer 28. It should be noted that the timers 10, 12, 14, 16 and 20i, the control logic 18 and the tone generator 24 could be mechanized; as part of a single microprocessor br not 100, which is! ;: I i appropriately programmed to achieve the desired functions. As an example, a single-chip microprocessor is available that may find application here with chip number! ;! COP 411, manufactured by National Semiconductor Corporation. i ;The circuit details of the block diagram illustrated in fig!, lj<:>are described with reference to figures 2 and 3 in the drawing. Referring first to the schematic circuit in fig. 2, the voltage comparator 6 is shown connected between! the diode bridge 4 and the chip control circuit block 100 in fig. 1. The voltage comparator 6 is of a conventional design, and the details of this are therefore not discussed in more detail. As those skilled in the art will be familiar with, the comparator 6, however, often comprises an amplifier 32 with a pair of input terminals, by means of ! i ;• of which the telephone line's voltage can be compared with a I i I reference voltage (approx. 5 volts 1ike voltage) , which is denoted-! in mains Vcc. The amplifier 32 is adapted for coupling by | approx.:<1>15 volts direct voltage, so that the level of the output signal from there j i i \which is emitted to the chip control block 10 is suitable to give an I indication of the condition of the telephone fork contacts (released electricity- ' I ! i lei r depressed) .! ! ii ;I ;The telephone holding circuit 22 is connected between an output terminal 33 of the bridge non-controller block 100 and a common electrical connection 34 which is formed between the diode bridge 4 and the voltage comparator 6. More precisely, the holding circuit 22 comprises: ■ in the !jinterconnection of a current limiting resistor 36, a ze- j ', nerve diode 38, the conduction path of an NPN transistor device 4 0 log a source of a reference potential1, such as ground. The current-limiting resistor 36 is chosen to simulate the dynamic impedance of the telephone when its circuitry is in the hold state. The zener diode 38 is a readily available voltage source, eg, Part No. 1N4744. , manufactured by National Semiconductor Corporation. Zener diode 38 has a breakdown voltage of about 15 volts direct current. Transistor switch 40 is also-i, so a readily available device, such as Part No. 2Ni 6719, manufactured by National Semiconductor Corporation.!!1 The base electrode of the transistor switch 40 is connected to the terminal]33 via a current-limiting resistor 42. The supply source for the reference voltage V"cc is also connected to the terminal 33 via an ordinary pull-up resistor 43. During operation, in the zener diode 38 the function of distinguishing between an off-hook state (ie when the fork contacts are released) and a holding state (where the telephone handset is placed back on the fork to press down the fork contacts) ). More precisely, the zener diode 38 is biased by the voltage at the usual electrical connection 34. As previously discussed, the electrical connection 34 is driven to a significantly higher voltage (approx. 50 volts ), when the phone's fork contacts are pressed down, than the voltage (about 6 volts) on it reaches the fork contacts; is released. Consequently, the zener diode is forward-biased to j enter the conducting position whenever the phone's fork j contacts are pressed down (ie when the phone's handset is placed back on the fork). Furthermore, the zener diode 38 is reverse-biased to enter the non-conducting state whenever the fork contacts are released (ie, as when the telephone handset is lifted from its fork). The transistor switch 40 is made conductive when its base receives a relatively true logic level signal from the output terminal 33 of the chip control block 100. The telephone circuits are put into a hold state when the zener diode 38 and the transistor switch 40 become 1 conducting both, thereby clamping the electrical connection 34 close to ground via their respective wire paths. As those skilled in the art will understand, the holding circuit 22 is consequently only released when the phone's fork contacts are pressed down or the telephone handset is placed back on the fork and when a relative | true logic level signal (denoted HOLD in Fig. 1) is applied! the thyristor switch 40 from an output terminal 33 for the chip control block 100. The tione amplifier 26 comprises a zener diode 44 and an appropriate NPN transistor switch 46. The zener diode 44 and the transistor switch 46 are conventional devices. Eczema-j ;pNa; etlvioins akl an Semtriaconnsdiusctotorer n Co4r6 poværare tidoenl . nZren. er2dN3io9d0e4n, s pr4o4 dulesdernt I I ingays1i path is connected across the wiring path of the transistor switch 46, between a normal electrical connection 48 and a source for reference potential, such as ground. The zener diode 44 has the function of protecting the transistor switch 46 against transient voltages that could occur when ringing signals are applied to the subscriber line. An output signal (denoted TONE in Fig. 1) is printed in the chip control block 100 based on transistor switch 46 via a current-limiting resistor 47, for controlling its conductivity. ;! The output terminal (ie the electrical connection 48) for the tone amplifier 26 is via a coupling capacitor 50 connected to one end of a first winding which forms an audio output transformer 28. The other end of the first winding is connected to a ;I ;source for reference potential1, such as ground. One end of a second winding for the audio output transformer 28 is connected to the circuit line 5, and the other end of the second winding is connected via a coupling capacitor 52 to the circuit line 5'. The audio output transformer 28 is of conventional perform I see, j: such as the one characterized by 250 ohm - 8 ohm trans-; format developments. The function of the audio output transformer 28 is ;! to connect an audio signal from the output terminal 48 for the tone amplifier! ker 26 to the circuit lines 5 and 5', so that both the caller and the receiver of a telephone call are able to receive the desired signal indicating that the telephone circuit is being placed on hold. edkankon ipnglseeet nte tteis 5 l oi g et en 5v' eslftkoikr jkenofnot rtmaekoldt iugglfoe-r nsdtøe ept stkeeol lenv3foe0nn. ssMtjoyodrnueeal lnt sottirøedpl-se-- ;fjntättrend (not shown). Another module plug (not shown) yer connected to receive TIP and RING conductors 2 and 21 from the subscriber line. The latter module plug can be inserted into a socket for the above-mentioned telephone adapter. 1ale-I i- r- * ■ -<j>f<p>nadaptive joint can then be easily installed in a nen-1 |. si;kt is forged into a container which is usually placed on the back of the Itelefonhuset. Thus, the present telephone control device can be appropriately connected at the subscriber's line to each telephone that is part of the subscriber's telephone network. Due to the modular connection of the present control device with the subscriber line, it is not necessary to re-connect the wires or modi-ii ;ffeislelre e vaed bomnnaengnte enks jetntee lefteonleerfo, nsstlyirk edaenot rdgnjeirngne erh. ar Devt erskt atl idl-og

It is noted that the modular telephone plug 30 can be eliminated, so that the circuit wires 5 and 5<1> can be connected directly to the ! Idea wires that form the subscriber's telephone line.

i The mechanization of the logical control block 18 according to fig. 1 is now described in detail with reference to fig. 3. The output signal from the timer 10 (in Fig. 1) is applied to a conventional inverter 50. The output signal (denoted OPEN) - from the inverter 50 is applied to an input terminal for a 2j-input AND gate 52 and an input terminal (denoted J) for a| in conventional JK bistable flip-flop 56. The output signal (denoted

; r IMPULSE DELAY) from the timer 14 is applied to a second input terminal for the AND gate 52. The output terminal from the AND gate 52 is connected to an input terminal for a 2-input terminal AND gate 54, an input terminal (designated J) for one

another JK bistable flip-flop 70, and the input terminal of an inverter 62. An output terminal (denoted Q) of the bistable flip-flop 70 provides an output signal (denoted a 1 IMPULSE) to the other input terminal of the AND gate 54. The output terminal of the AND gate por- J

ten 54 is connected to both a second input terminal (designated i

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! J) for the bistable flip-flop 56 and to an input terminal j ; a 2-input terminal AND gate 58. The output signal from the digital differentiator 12 (in Fig. 1) is applied to both other input terminals for the AND gate 58 and a clock terminal (designated CLK) for the bistable rocker 56 to provide synchronous control of this. The output terminal of the AND gate 58 is connected to the input terminal of an inverter 60. The output terminal of the inverter

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the rectifier 60 is connected to an input terminal for the tone generator 24. The output signal from the time controller 20 is applied to the input terminal of an inverter 68. The output signal from the inverter 68 is applied to a delete terminal (designated CL<p>J)

'for the bistable flip-flop 56, since energization of first nejvn- j

■te is suitable for resetting the bistable rocker 56.

; iUi tgang terminal (denoted Q) of the bistable flip-flop 56 eri|<!>coupled for issuing an output signal (denoted HOLDFF) to

one of the chips that form the time control 20. A second output

!clamp (denoted Q<1>) for the unstable flip-flop 56 is connected; to emit an output signal to both the other chip which form- i ! in the timer 20 and an input terminal for a 2-input terminal;

•me AND port 64. The output signal from the inverter 62 is applied to the second input terminal for the AND port 64. The output signal from the AND port 64 is applied to an inverter 66. The output signal (denoted HOLD) from the inverter 66 is applied holding circuit 22

(most clearly shown in Fig. 2). The output signal from the digital differentiator 12 is also applied to a clock clamp (designated CLK) for the unstable flip-flop 70, in order to establish synchronous control thereof. The output signal (denoted 4 SEK) from the timing control 16

(in fig. 1) a delete key is pressed (denoted CLR) 'for ; the bistable rocker 70 to reset the bistable i

in flip-flop 70. A relatively positive source of reference potential !'V^c is applied via a current limiting resistor to both eh ! input terminal (designated PR) for the unstable flip-flop 56 and ! i<1>

.respective input terminals (designated PR and K) for the unstable rocker 70. I i i '■ i The JK unstable rockers 56 and 70 can for example be mechanized ! .. in ...!

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of conventional semiconductor chips, such as chip No. 74 1091,

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■ manufactured by National Semiconductor Corporation, where one-half of it is used to realize the flip-flop 56 and the second half is used to realize the flip-flop 70. Furthermore,

i!her of the above logic gates mechanized by conventional transistor-transistor logic (TTL) techniques. ! in 1! in

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The operation of the control circuit and logic described here and the procedure for triggering the hold circuit 22 for the purpose of putting an existing call in the hold state shall be described with simultaneous reference to figures 1 -4 in the drawing. More! in precise, illustrates fig. 4 the output signal levels in relation to j : time, of certain components that form the present telephone control device when its holding circuit 22 is triggered and a tele-j

• fb call is put on hold. Generally speaking and as previously discussed, the holding circuit 22 can be triggered and blocked each time the fork contacts 3 and 3' are operated to produce a sequence of two fork pulse signals within a 4 second interval. In the present example, a fork impulse is | .signal defined by depressing the fork contacts 3 and! 3', 'so that the output signal (denoted SWHOOK) from the comparator 6i ! has a relatively false logic level in a time interval greater than 150 milliseconds but less than 750 milliseconds. As illustrated in fig. 4a, the SWHOOK signal has 72 eti re-r ;latively true logic level (e.g. +5 volts direct current) eachj ! time the handset is lifted from its fork and the fork contacts 3 and 3' are released. The SWHOOK signal has a relative i 1 i .false level (e.g., ground) during the generation of fork pulse signals 74 and 76. After the prescribed sequence of i ■fork pulse signals 74 and 76 is generated, the user puts ; the handset back on the hook, at which point the 77<:>SWHOOK signal again has a relatively false logic level and the hold circuit 22 is triggered and blocked. The holding circuit 22 will j ,remain blocked for a maximum of 6 minutes after the generation of the j second hook pulse signal, until the user either lifts the handset from the hook (thereby resuming the telephone conversation): i , i

or until 6 minutes the time control 20 strikes time-limiting; lut to reset the rocker 56 and thus automatically terminate the holding condition. If the holding circuit 22 with second

In other words, if the latch remains for a period of time in excess of 6 minutes, timer 20 will be activated to provide a signal both to reset flip-flop 56 (at its CLR input terminal) and to cause deactivation of latch circuit 22 :(via AND gate 64) by means of a signal of relatively true logic level which is then formed at the Q' output terminal foi' jflipper 56. Certain warning signals generated from the central I jle ■. station can also end the hold state. As most clearly illustrated in fig. 4g, the flip becomes 56 at the end of i

second fork pulse signal 76 set so that it forms the output signal HOLDFF with a relatively true logic level 94 to thereby trigger the 6 minute timer 20.

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As illustrated in fig. 4b and as previously discussed, the output signal OFHOOK from the delay device 8 is delayed by

■an interval 78 of approx. 150 milliseconds in relation to the generation of the SWHOOK signal from the comparator 6. Thus, the OFHOOK signal has a relatively false logic level 150 milliseconds after the fork contacts are depressed (ie on)

and the SWHOOK signal correspondingly goes to a false logic level. Furthermore, the OFHOOK signal has a relatively true logic level

(substantially at the same time as the SWHOOK signal) when the fork ■contacts are then released (ie are off). Because OFHOOK! i the signal is to have a relatively false logic level, the SWHOOi K signal must be continuously false for at least 150 milliseconds.jj Any possible jump in the SWHOOK signal to a relatively true logic level sets the 150 millisecond delay backji the OFHOOK signal. Thus, the delay device 8 acts as a timing control to create a lower time limit (eg, 150 milliseconds), the duration of which must be exceeded by a fork pulse signal in order for the particular sequence to! is completed correctly.'

As illustrated in fig. 4c and as previously discussed, the output signal from the inverter 50 (whose signal level is inverted in relation to that of the output signal from the timing control 10) has a relative ivti! true logic level after the OFHOOK signal has had a rela-

( - i ;tive true logic level continuously for one second. OPEN signa-' . i second. j

IN

:let has a relatively false logic level after the OFHOOK signal has had a relatively false logic level continuously for one second. Therefore, any transient change in the level of the OFHOt>K 1 signal has the effect of resetting the 1-second delay in the ON-!NE signal. The above 1-second intervals are represented by the reference numbers 80 and 82 respectively. The holding circuit! :22 can thus only be triggered when the OPEN signal has a relatively true logic level.

<1>i As illustrated in fig. 4d and as previously mentioned, develops! i IMPULSE DELAY out signal from the time control 14 monopul-! see 86 and 88, which have a relatively true logical level each time

i I i ! ■ga' ffel contacts are pressed down for longer than 150 miliii-■seconds. As a result of the triggering of the time control 14 by means of the delay device 8, the generation of! the monopulses 86 delayed by a 150 millisecond interval (denoted by reference numeral 84) relative to the generation of the SWHOOK fork pulse signals 74 and 76 in FIG. 4a. !IN

.IMPULSE DELAY the signal thus induces 750 millisecond delays which time the respective fork impulses. signals. If a fork impulse signal1 thus exceeds 750 milliseconds (e.g. with the fork contacts in a depressed state), the time control will thus limit the time, so that

'a relatively spurious PULSE-DELAY signal is then emitted both to deactivate the hold circuit 22 (via AND gates<i>52 and 64 ) by a corresponding relatively spurious HOLD signal and! j to ij

in maintaining the logic state of the bistable flip-flopsj 56

.and 70 (by grounding their respective J input terminals).

: i l'As illustrated in fig. 4e and previously discussed, the 4 SEC output signal from the 4 second timer 16 has a relatively true logic level of 90 approx. 150 milliseconds after generating the ! 'first fork pulse signal 74. The 4 SEC signal has a width of 1 I for 4 seconds, after which a relatively false signal is created.

: i Therefore and in the event that the sequence of fork pulses 74 and 76 i is not completed within the 4 SEC signal's 4 second inter-

i vall, a relatively false logical level signal is applied by the I I tii ds control 16 to the CLR input terminal of the flip-flop 70, fojr

IN

thereby resetting the flip-flop 70 so that it is responsive to the initiation of a new fork pulse signal sequence.

ij in So!m illustrated in fig. 4f, the bistable flip-flop 70 emits an output signal (denoted 1 PULSE) from one of its output terminals Q to an input terminal J of the bistable flip-flop 56 via AND

gate 54. The 1 IMPULSE out signal has a relatively true logic level upon completion of the first fork pulse signal 74. The flip-flop 170 is set via the AND gate 52, upon receipt of a pulse with a relatively true logic level at one of its entrance cloak-! :me1 r J, when the first fork pulse signal 74 is generated. Dier-for stores the rocker 70 a hint that a first gaffeir

i [i5m4 puinlnssstiginlat l of has a fusningenat l smteedd . rVeilappteivn t 56 sabnt lir lovgiia sk OG nivpoå rvtekd n |j jvippens J input terminal, when the second fork impulse sighal [is generated within the 4 second interval (created by the 4 second timer 16).

! y! As illustrated in fig. 4h, an output signal from the output terminal Q' of the flip-flop 56 is applied to the hold circuit 22 via the AND gate i■64 and the inverter 66. The output signal, designated HOLD, from the inverter 66 has a relatively true logic level 150 milliseconds after the first fork- Impulse signal is generated

■ (ie when the OFHOOK signal assumes a relatively false logical nine-two). During the interval, which lasts for 750 milliseconds and' is j ;denoted 96, after the first fork Pulse signal is set

in operation, the circuit 22 assumes a momentary hold state until it can be determined whether a second hook pulse signal has been generated or the telephone receiver has otherwise been placed on the hook for

; I I

enable the user to terminate an existing call.! The HOLD signal assumes a relatively false logic level (denoted!

i l 98) 150 milliseconds after the completion of the first fork-J pulse signal 74. the HOLD signal again assumes a relatively true [ ;:■ logical level when the second pulse 86 of PULSE-DELAY si ig-I

nal is pressed AND gate 52. After the sequence of gaf- ! : if electrical impulse signals 74 and 76 are correctly completed, the user hangs up, at which point (symbol 102) the zener diode 38 and the transistor 40 of the holding circuit

22 is made conductive by the relatively true level of the HOLD signal, whereupon the hold circuit 22 is triggered and inhibited (at : ' 56) i by means of the flip-flop 56) for a present call to be set ! ij holding condition for a maximum of 6 minutes. The holding state slips! :also solved when the user removes his hook from the fork or in when the OFHOOK signal assumes a relatively true logic level while in the OPEN signal assumes a relatively false logic level. i As illustrated in fig. 4i, upon completion of the second fork impulse signal 76, a tone burst 103 or an audio signal (designated TONE) is generated by the tone generator 24. The tone burst preferably comprises sixteen 50 millisecond pulses or a 2 kl-Iz square wave. The interval between pulses is approx. 100 : milliseconds, so that the envelope is square. The tone interruption can be generated with the hold circuit 22 triggered and blocked, so that an additional audible signal is pressed every time an attempt is made to put an existing call on hold. <;>i ■The drawing's fig. 5 illustrates the output signal levels, in relation to time, for some of the components that make up the present ; holding device, when an incorrect fork electric impulse signal sequence is initiated (e.g. due to an accidental depression of the fork contacts), so that the hold circuit 22 is not released and a present call is not placed on hold . More precisely and with simultaneous reference to fig. 1-3 and, 5, the SWHOOK signal has a relatively true logic level 104 after the handset is lifted off its fork and the fork contacts i i 3 and 3' are released. But only one is generated! fork impulse signal 106 within a time interval of 4 seconds. Accordingly, the PULSE-DELAY signal contains the ba-! re a single monopulse. Furthermore, the output signal HOLDFF from the flip-flop 56 never reaches a relatively true logic level, inasmuch as the second fork pulse signal is not generated until the flip-flop 70 is reset by the 4 SEC output signal from the timer 16. In addition, 4 SEC and 1 The IMPULSE signals can assume<i>cent signals with a relatively true or false logic level j110 or 112 or 114 or 116, depending on the time thatj passes (in relation to 4 seconds) before the snooze becomes lag t-down-on-ga-r f e- len again. Consequently, the HOLD signal has a relatively true logic level only during 750 millisecond intervals after the fork contact is depressed and a momentary hold signal is stopped.

is created. When the user places his nap back on the fork (represented by reference numeral 108), the HOLD signal has a relatively false logic level, so that the transistor switch 40 for the holding circuit 22 is not made conductive. Consequently, the holding circuit 22 is not triggered, so that the telephone i

1

the user, instead of putting an existing call on hold as described in connection with fig. 4, orjs terminates the current call when the user's nap is placed on the fork.

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It will be obvious that although a preferred embodiment example has been shown and described, various modifications and changes can be made without deviating from the true spirit and scope of the invention. When a preferred embodiment of the present invention has now been described, the following claims are presented:

Claims (1)

li. For a telephone (1) a device for controlling the operation of the telephone, where the telephone has fork contacts (3 and 3') which are interfaced to transmission lines (5 and 5') so that fork impulse signals can be transmitted via them, said telephone control apparatus responding to a specific sequence ay fork contact generated fork impulse signals to activate a hold circuit (22) to set an existing call in; holding state, as said control device is characterized by a signal detector (6), connected to said transmission lines for recording whether the fork contacts for said telephone are either in depressed or released state, where the detector forms an output signal j (SWHOOK), the level of which depends on the state of the said fork contacts, and a st <y> relogic (18) connected between said signal detector and said holding circuit, where said control logic is operated in response to out - the signal from said detector, when the fork contacts for said telephone are in a depressed state in: specific time intervals, where said control logic danni is <:> ! a control-out signal (HOLD) to activate said hold circuit and thereby put an existing call in the hold state etjter j completion of said particular gaf f electrical impulse signal sequencej. 2.Telephone control device as stated in claim 1, characterized in that said telephone comprises TIP <p> g j RING conductors (2 and 2'), where said fork electrical contacts (3 and j 3 1 )| is connected, where said transmission lines (5 and 51 ) are connected to said TIP and RING conductors, to receive fork- i I I the impulse signals generated by the fork contacts. j j 3. Telephone control device as stated in claim 1, k a r a ki - ;! te r'ized by the control logic (18) includes mid- i ler (56 and 70) for counting the number of fork electrical impulse signals| ] i which is transferred via the transmission lines (5 and 5'), where the control logic forms said control-out signal (H OLD ) for activation of the holding circuit (22) after the number of fork impulses < 1> in signals counted corresponds to the number of fork impulsesig- 1 1 nals that form the particular signal sequence. In 4,. Telephone control apparatus as stated in claim 3, clause K--Iterated in that said means for signal counting I includes at least first and second bistable flip-flops (56 and 7j 0) I which are interconnected, where the first bistable flip-flop (70) : receives and stores an indication of a first fork electric impulse-; signal (74), and said first bistable flip-flop activates While the second bistable flip-flop (56) reaches the first bistable flip-flop. I receives an indication of a second fork impulse signal (76), in which the second bistable flip-flop produces a corresponding ' ' i , signal to thereby enable the formation of the control-out signal : (H OLD) for triggering the holding circuit (22 ). j i 1 I I i it5l;. erTiesleef ornst tyrevapepad rat en as tidansgstiytrt ini g kr(a2v 0) 3, , which k a is r so mmijk en-- ; i. k; opled with the control logic (18), where the time control is un.!t-I resolved after completion of the determined sequence of fork-i i1 | impulse signals, and where the timing control produces an output signal after a certain period of time to bring the counting device; 'gen (56) to restart the fork pulse signal count and the control logic to close the hold circuit (22) in case said board has not been closed previously. j i 6. Telephone control device as specified in claim 3, characterized by a time control (16), which is connected to the control logic (18), where the time control is triggered by a first fork pulse signal, and where the time control in-iI gene produces an output signal (4 SEC) after a certain time' for i 1 I ;å; causing the counting devices (56 and 70) to start their ! fork pulse signal counting again in the event that the specified sequence of fork pulse signals is not completed within the specified time period. i ' <i> j i <!>' 7. Telephone control apparatus as specified in claim 1, characterized by indicating means (24, 26), which are connected to the control logic (18) to receive control output signals! ;(TONE) from there, where the indicating means emits an audio signal 'to the transmission lines (5 and 5') to give. an indication..there.-. In that the hold circuit has been released and an existing call has been put on hold. IN ! in 8 <\> . Telephone control device as set forth in claim 1, characterized by a delay device (8), which is connected between the signal detector (6) and the control logic (18), where the delay device works so that it prevents the transmission of a fork impulse signal to the control logic, when the length of the fork impulse signal is less than a determined time, where the determined time corresponds to the smallest time at which a fork impulse signal can be generated to correspond to the determined signal sequence. 9; i . Telephone control device as specified in claim 1, characterized by a time control (14), which is connected to said detector (6) and reacts to the length of! the fork impulse signals when the fork contacts (3 and 3') are in the depressed position, where the time controller emits a signal (IMPULSE DELAY) to the control logic (18) to prevent acti i-! vising the holding circuit (22), when the length of the fork f el-impI uls-;! the signal is greater than a certain time, which certain time j corresponds to the maximum time during which a fork f el-imp^ls-l ■ signal can be generated to respond to the particular signal sequence. i I i i 1■ 0. In a telephone network comprising at least one telephone (1), which has fork contacts (3 and 3') for generating fork i 1 impulse signals and a telephone control device (22), which is adapted to for selective activation of a distinctive and specific sequence of at least two user-triggered fork pulse signals,j for! : control of a function of the telephone, a control circuit (100)1, j i i which is connected between the fork electrical contacts and telephone control! ean-;1 In the scheme and reacts to the user-triggered fork impulse sig- .nals, where the governing circuit is characterized j v; e d counting devices (56 and 70) for counting the number! user-triggered fork pulse signals, where the counting devices ' i i emits an output signal for activation of the telephone control device, when the number of fork impulse signals counted corresponds to ■ i ! I to a predetermined number, a first timer I (16) for measuring the time interval for completion of the pre-fat • and second fork pulse signal, wherein the first timer is coupled to the counter means for outputting a signal (4 SEC) to the counter means to cause the count to be restarted when the interval measured by the first 'time management is greater than a predetermined time, and one in 1 i second timer (8 or 14) responsive to the length of I each of said first and second fork pulse signals, where i jde: n second timer is coupled with telephone control ah1 word <-> Ini■ ngen to prevent activation of the control device whenji the length of a fork impulse signal is either shorter or shorter than the respective fixed times. in i i 11. Telephone network, as stated in claim 10, where the control circuit is further characterized by an additional time controller (20), which is selectively activated upon completion 1 'o of the determined sequence of fork impulse signals to measure In the subsequent time, where the additional time management is connected ij:" ot" ridl ntienglen eanog orddnerimnged en fø(r5e 6) tfiol r aå t advegni s etet lsliigng nal statril ter teolplepai;pnå- o; ii new and that the telephone control device (22) is deactivated when the time measured by the additional time control is longer than a predetermined time. j i i 12. Telephone network as specified in claim 10, where the control circuit is further characterized by an additional time control (10), which reacts to the depressed and released positions of the fork contacts, where the additional time control is coupled with the telephone control device (22) for to: emit an output signal (OPEN) to prevent activation of the control device in case the fork contacts have been in released | position for less than a specified time before the specified sequence of user-triggered fork impulse signals takes place|, ! ■ l I ;where the additional time control prevents inadvertent activation j jav the control device as a result of bouncing or randomly I reciprocating fork contacts. i !. in . J <:> 13. Telephone network as stated in claim 10, where the second time-i = I control is characterized by a signal delay device (8), which is connected between the fork-kbn-I beats (3 and 3 <1> ) and the first timer (16), where the fpr-: zincing device responds to the length of the fork-im <p> ulp- ■signals to prevent transmission of the fork-impulse signals ;to the first timer in case the length of a fork-im- ■pulse signal is shorter than a fixed time. I i <1> ' ' I |l4. Telephone network as specified in requirement 10, characterized in that the second timing controller (14) reacts to the length of the fork pulse signals, where the second timing controller is connected to emit an etj out signal (IMPULSE DELAY) to the telephone control device (22) and to the counting devices (56) and 70) to inhibit the counting of the counting devices and activation of the control device when the length of a fork impulse signal is greater than Ln determined time. J I i i 15. Telephone network as stated in claim 10, j characterized in that the telephone control device comprises a hold circuit (22) which is connected between the control circuit (100) and the telephone (1), where the hold circuit is adapted for selective activation to put circuits of the telephone in hold state when the particular sequence of bru- | ker-triggered fork impulse signals are completed within a ! fixed time. in ! ! in 16. Telephone network as stated in claim 10, genes (56 and 70) comprise at least first and second bistable ^ j flip-flops which are interconnected in the control circuit (100), where it: first bistable flip-flop (70) receives an input signal indicating-! i i rer generation of a first fork impulse signal, where first bistable flip-flop emits an output signal for activation of the I in the second bistable flip-flop (56), when the first bistable flip-flop receives yet another input signal indicating the generation of a j second fork electric impulse signal, and where the second bistable flip-flop, i i emits an output signal (HOLD) to thereby cause activation | i , ring off the telephone control device (22). 17. Telephone network as stated in claim 10, : characterized in that it further comprises : indication devices (24 and 26), which are connected between the control circuit (100) and the telephone (1), where the control circuit emits an output signal for energizing the indication devices whenj ! the special sequence of user-triggered fork pulse signals has been completed for activation of telephone control device nkn- ! gene (22), where the indication devices emit an audible |out — | ■ signal (TONE) to the telephone in order to indicate to a ■ user thereof that the special gaf f electric impulse signal sequence | 1 has been completed. 18. Telephone control device comprising a holding circuit 022) J which is adapted for selective activation by i [a particular sequence of user-triggered hook-pulse telephone signals to place an assigned telephone (1) on hold^ ,' so that the telephone receiver can be returned to the hook without' | disconnect an existing call, where the telephone comprises TIP and JI RING transmission lines (2 and 2') which are connected to a central telephone station and fork contactors (3 and 3')/respectively coupled together with the transmission lines for generation of fork -j fel impulse signals via these, where the control device is cop- | led to the telephone by the TIP and RING transmission lines and you characterized by signal detectors (e.g. ks.i 8, 14, 16, 56 and 70), which react both to the number of fork- | impulse signals that are generated within a certain time and for the j length of each of the aforementioned fork impulse signals, where the detectors form output signals (e.g. HOLD) for selective activation of the hold circuit and thus to put the telephone in a hold state when the length and the number of fork impulse signals generated corresponds to the particular signal)- ! sequence.